delete index file before writing to it (if change)

Otherwise, the file is writen in place and changes the hardlinked
ones too in older trees, therefore introduces inconsistencies in
older snapshotted trees.
Updated Translations New translation-codes for the i18n-directory. Related to issue #9. Removed translations: ast,eo,eu,fa,ka,oc because there are no offical languages in ISO-3166-1 alpha-2.
Run perltidy.
Document possible improvement of the translation file download.
Extract all translation files from the dists/$DIST/$COMPONENT/i18n/Index file.

Fall back to parsing dists/$DIST/Release if i18n/Index is not found.
Do not round bytes (we have no half bytes).
Fix typos.
Run clean script with "set -e" to check return codes.
Mirror Contents-*.gz for each component.

This fixes http://bugs.debian.org/647301
Also mirror InRelease files (fixes #3).
Do not try to read the index file if open failed.
Also download InRelease file if mirroring only source packages.
Print formated bytes in clean script.
Clean only directories that still exist.
Make clean script executable.
Replace the install script by a Makefile.
Run perltidy.
Update changelog for upcoming 0.5.0 release.
Spelling and grammar improvements

Thanks to Vincent McIntyre <vincent.mcintyre@csiro.au> for the patch.
Update changelog.